Am Std Heritage (Aquaseal) shower diverter not diverting

[Jim Oestreich]

I have a 50s era bathroom with near perfect ceramic and porcelain. So I am trying NOT to replace the Am Std Aqua Seal tube faucet with a fantastic plastic imitation. Problem is that I am not getting full shower flow when i turn the diverter to shower. I get about 30-40 % of the flow into the spout. I replace the seat and washer but now change in flows. Wondering if there is an alignment required for the holes in the barrel of the stem assembly. I am missing something here.

Any help would be appreciated!